The present invention relates to a scaffolding arrangement and, more particularly, to a perforated connecting disk for scaffolding elements, with the perforated connecting disk being adapted to be fastened on vertical scaffolding elements such as, for example, upright elements, bracing elements, intermediate parts, and/or other special elements, and with the perforated connecting disk enabling the connection of wedge-shaped tapering connecting heads with push-through wedges.
Perforated connecting disks provided with wedge holes of different sizes such as, for example, alternately large and small wedge holes have proven effective for some fifteen years in scaffolding arrangements and, in the perforated connecting disks, a smaller of the wedge holes generally has a contact area at an outer circumference thereof which is flat and vertical in an installation position, with the contact area or surface being wider than a thickness of the wedge only by an amount of play required for the installation, and with the remaining limits of the contact area being convex.
High strength perforated disks are required for connecting devices of scaffolding elements and, for this purpose, on each of the outer edges of the holes, a wedge contact surface is formed against which the wedge abuts, while an inner edge of the wedge hole plays no role in exact positioning. For a well-aligned assembly, it is especially advantageous to precisely angularly limit the contact area of at least a few wedge connections.
For this purpose, in, for example, DE PS 24 49 124 corresponding to U.S. Pat. No. 4,044,523, a scaffolding arrangement is proposed wherein a ring flange is provided with spaced cutout which are substantially oval in configuration and are so arranged that the longitudinal planes of symmetry intersect one another in the longitudinal axis. The cutouts are provided with blunt ends bounded by planar faces, with the planar faces being arcuately curved on an arc whose center coincides with the longitudinal axis. The faces can also be curved in an axial direction of the ring flange so as to obtain a particular advantageous engagement with the wedge member. The dimensions of the faces in the tangential direction correspond to the dimensions of the wedge member to be inserted so as to assure a proper seating of a free end of the respective bracing element against the respective vertical or upright element.
Recently the demand has increased for lighter scaffolding primarily in the case of rapid assembly for use by workmen and, especially in industrial applications such as, for example, when scaffolding must be inserted into interiors of boilers, scrubbing and decontamination equipment, and the like in a short period of time and through relatively small openings. In view of this demand it has been found that scaffolding elements can be made of a relatively light metal. Standardized scaffolding is restricted to certain compulsory dimensions for all of the elements that are mutually interchangeable and, for this reason, the acceptable loads are often sharply restricted by the properties of the material and the specified dimensions.
The areas around the wedge holes generally constitute areas where forces are applied and transferred and such areas are employed to optimize the stress forces and working loads.
In, for example, DE-OS 37 02 057 and corresponding U.S. Pat. No. 4,867,274, a light metal scaffolding is proposed; however, in this proposed scaffolding, conventional hole shapes are utilized and the proposed arrangement attempts to take advantage of play during installation and assembly as well as certain tolerances within a possible range. However, no deliberate effort is made to influence the stress patterns in the perforated disks.
U.S. Pat. No. 4,493,578, also proposes a scaffolding connector and system wherein brackets in the form of locking rings are provided with the brackets including a plurality of cutouts each having a bearing surface disposed at a common maximum radius so that a connector can be effectively mounted in any one of the cutouts and be functional with respect thereto. An inner circular arc defines an opposite face of each of the cutouts and is preferably disposed at the same minimum radius or at least a sufficiently small radius to prevent the bearing surface of an accommodated wedge from engaging that surface when in an operative position.
In, for example, French Published Application 2,553,456, a scaffolding arrangement is proposed which includes a ring having a plurality of radial arms disposed at 90 degree intervals with each of the arms having a radial cutout triangular in shape and having a rounded vertex and base. Lateral contact surfaces are disposed above and below the base of each of the radial arms, with the lateral contact surfaces being separated by a radial incurvation designed to serve as a locking support for front faces of branches of a connecting plate.
The aim underlying the present invention essentially resides in providing a perforated disk arrangement for scaffolding which avoids, by simple means, shortcomings and disadvantages encountered in the prior art and which enables a propagation and transfer of forces and stress patterns in a predetermined manner thereby increasing an acceptable level of stress forces and working loads for the scaffolding.
In accordance with advantageous features of the present invention, a perforated connecting disk for scaffolding is provided wherein entire hole limits of the small wedge accommodating holes, with the exception wedge contact surfaces, form a continuous curve with no discontinuities, which is symmetrical with respect to a radius passing through a center of the wedge contact surface.
While conventional perforated connecting disks were provided with a plurality of holes for accommodating the wedges, the holes were made with sharp edges even in areas near the upright elements since it was desired to guide the wedges by means of the edges of the respective holes; however, after a considerable length of time and contrary to previous assumptions, it was discovered that by improving the shape of hole edge in an area near the disk at points where the cross sections are the thinnest and by avoiding sharp corners, a significant improvement can be realized which is significant for light metal construction if a non-discontinuous shape is selected for the edge of the hole.
Thus, in accordance with the present invention, the entire hole limits of the small wedge holes, with the exception of the contact surface form a continuous curve which is symmetrical with respect to the radius passing through the middle of the wedge contact surface.
A curved shape of the hole boundary of the small wedge holes may, in accordance with the present invention, be approximately oval shaped markedly tapering at one end thereby resulting in small wedge holes being approximately of a pear-shape, with an inner area which is nearly cylindrical and faces the center, which area makes a continuous transition to side areas with a larger radii.
Depending upon the constructional features of the edge areas and direction of forces in the perforated connecting disk and transfer to the upright element, it is also possible to provide a slightly modified construction in which the wedge contact surface remains in the form provided and the remaining line pattern remains continuous and non-discontinuous.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawing which shows, for the purpose of illustration only, one embodiment in accordance with the present invention.